1. Field of the Invention
The present invention relates to a radio paging system using a radio selective paging receiver and, more particularly, to a radio selective paging receiver designed to directly receive a radio wave from a relay station in an MCA system.
2. Description of the Prior Art
As a mobile communication means, an MCA (multi-channel access) system is widely used. This system is designed to realize radio communication between a fixed station and mobile station or between a given mobile station and another mobile station via an MCA relay station. For example, the system allows communication between an office as a fixed station and a vehicle as a mobile station or between vehicles.
Assume that a callee in a vehicle having a mobile station moves to a desired place, and he/she leaves the vehicle to do some work. In this case, since the radio communication unit of the mobile station is fixed on the vehicle or relatively large, the callee seldom leaves the vehicle carrying the radio communication unit. For this reason, a caller cannot reach the callee while the callee stays at a predetermined distance or more from the vehicle.
If the callee carries a radio selective paging receiver which can be called through a general telephone line, the caller can reach the callee even if the callee leaves the vehicle. In this case, however, the caller must pay a telephone line charge to call the radio selective paging receiver.
Japanese Unexamined Patent Publication No. 4-49724 filed by the present applicant discloses a radio paging system using a radio selective paging receiver for receiving a radio wave from the radio communication unit of a mobile station. In this system, a callee carries a radio selective paging receiver when he/she leaves a vehicle so that the callee can be called through the radio selective paging receiver designed to receive a radio wave from the radio communication unit of the mobile station when another calls the mobile station.
In the radio paging system disclosed in Japanese Unexamined Patent Publication No. 4-49724, however, when the mobile station receives a radio wave from another station via the MCA relay station, the radio communication unit of the mobile station outputs a radio wave for calling the radio selective paging receiver. According to the radio law, however, the radio wave that can be output from the mobile station to call the radio selective paging receiver is limited, and it is difficult to ensure a radio output large enough to call the radio selective paging receiver carried by the callee. In some case, the radio selective paging receiver cannot receive the radio wave from the radio communication unit of the mobile station.